There are important applications for stimulated Brillouin scattering slow light in all optical communications network.The conventional optical fibers used as slow light medium have low delay efficiency,so the demands of fiber length and pump power are higher.The delay efficiency can be improved by using highly nonlinear photonic crystal fibers.The Brillouin gain of 33 dB is achieved in a 70 m highly nonlinear photonic crystal fiber under the pump power 101 mW,which results in 30 ns time delay of 50 ns signal pulses.The delay efficiency of this kind fiber is 0.0046 ns/(mW·m),which is about 13.7 times larger than the single mode fiber.The demands of fiber length and pump power are effectively reduced when this kind of fiber is used,and the fiber has a large potential use in stimulated Brillouin scattering slow light system.